It has been widely acknowledged that Plato is the most significant and stunning figure in the establishment and development of philosophy and science, especially in western culture and society. Unlike other philosophers, Plato’s works and thoughts have influenced a long history—over 2400 years. He invented the dialogue and dialectic forms in describing philosophy, such as his work Republic and Laws, giving clues about the ancient philosophical perspectives on politics, science and religion and so on. As for his student—Aristotle, he was also considered one of the most important philosophers, scientists and educationists, making profound contribution to almost every subject. Aristotle’s twenty years in Plato’s Academy was decisive years for his study and life. It is recorded that Aristotle is not a person that entirely worships authority but develops his own independent thinking.

In this paper, the author would like to conclude Plato’s views on the nature of knowledge and natural science with the reference from Timaeus. Furthermore, this paper would also analyze how Aristotle’s inheritance and development in the subject of nature, especially on physics.

The nature of knowledge

In many Plato’s dialogues, he described Socrate’s ideas that the essence of knowledge is recollection rather than learning, observation or study. Plato himself supported that knowledge comes from natural talent, which exists in the human soul in a potential way. In other words, he thinks that knowledge is not a spontaneous feeling or response towards the outside material world, but a recollection of idea world. Consequently, when his thought on nature of knowledge reflected in education, Plato claimed that purpose of teaching is to restore human being's inherent knowledge. In the teaching, he puts high emphasis on general and universal understanding, especially paying attention to the cultivation of student’s thinking ability. He argues that conception and truth are production of pure mental process. At the same time, he points out that students are able to recall the idea of world through the shadow in real world reflecting from the idea one. Since things which students encountered and contacted in the early childhood have long influence for his life, he believed that the teaching process should pay attention on stimulating student’s memory by concrete materials and repeated reflection and then inspire the inherent ideal knowledge.

Plato pointed out that the world is consisted of “the concept world” and “the phenomenon world”. The former is a real and permanent existence, while the latter is merely image from the idea world. The phenomenon world is not consistent since it was made up of temporary phenomenon changed by time and space. He illustrated his point by employing the famous example—the Allegory of Cave. In his dialogue, he mentioned reflection and contemplation for many times. Accordingly, he developed a perspective concentrating on ideology and recollection, making it the philosophical basis of teaching theory.

Plato holds the view that the tangible things in nature are flowing while the form or idea that constitute these materials is eternal. For instance, when people are talking about “horse”, they don’t necessary refer to a particular one, instead it is a general conception. And the definition of “horse” is independent from all kinds of visible horses, which do not exist in space or time spam yet it is eternal. But a particular horse, which does exist in people’s mind, will die and decay in the end. This could be regarded as a preliminary explanation of Plato’s theory of ideas. He argues that as for the apparent and changing things, instead of having a true perception, we could only develop opinions or views. The only thing that we can truly understand is those that we utilize our rationality. Therefore, he concludes that there is no possibility that knowledge is wrong since it is fixed and certain. Only opinions may be wrong.

Plato’s universe view in Timaeus

Plato attempts to make astronomy a branch of mathematics. He believes that both the research of astronomy and geometry can be conducted by raising problems and solving problems. According to Plato’s argument, the genesis of cosmos itself is a chaos without distinctions. The opening up of this chaos is a result the activity of supernatural God. The reason why the universe becomes orderly from chaotic is because that the Creator developed a rational scheme.

Plato’s view of the universe is basically a mathematical concept of the universe. And this is illustrated in the book Timaeus. According to Plato, there are two kinds of right triangles at the beginning of universe, one is half of the square, and the other is half of equilateral triangle. These triangles generate four kinds of regular polyhedron, which is composed of four elements of particle---fire, water, gas and soil. The four elements are “the most excellent four bodies that can come into being” (53e). The whole universe is a sphere, because it is symmetrical and perfect and every spot on the surface is all the same. The movement is a circular motion, because the circular one is the most complete, calling for no push of hands or feet. The number of each four element in the universe is this: the ratio of fire to gas is equal to the ratio of air to water and the ratio of water to soil. Everything can be named by a number, which is the ratio of elements they contain.

Timaeus is the only one dialogue that Plato concentrates on discussing about natural philosophy. In the early and middle period of Plato, he did not make specialized statements on it. The problem has been left to Timaeus that Plato illustrates his perspectives in natural science completely. In Timaeus, the concept of God is not created but a natural god who makes the chaos orderly. The creator of Plato’s physical world is not a divine intelligence or a personal ruler, but (as it were) a manual laborer. Cf. Vlastos, Plato’s Universe (pp. 26-27): That the supreme god of Plato’s cosmos should wear the mask of a manual worker is a triumph of the philosophical imagination over ingrained social prejudice. However; this divine mechanic is not a worker. He is an artist.

According to him, God is good and never being jealous. Thanks of his virtue, he designs everything that looks like him. And this is the highest principle of the origin of the universe and the changing state. When he found out that the entire visible field is not in a static but in an irregular and disordered state of motion, he put the chaotic world in order because he believes that the state of order is better in the whole. Therefore, when God creates the whole world, he puts the rationality into soul, and soul into body. In this way, his productions are the best and most perfect in essence. This statement has profound and long term influence on the medieval philosophy and even the thinkers in the Renaissance. Plato carries out a series of discussions to the material construction in microscopic world. Due to the limited development of natural science in history, his understanding has long received injustice comment. However, with the improvement of modern physics, especially the growing integration of mathematics and physics, people started to realize the common aspects between geometry and modern natural science.

In conclusion, in the Timaeus, Pluto describes the formation of universe in a detailed manner. Plato proposes that the universe is the handwork of a divine Craftsman who imposes an order on an existent chaos. As Plato puts it, the attractive orderliness of the universe is not only a display of Intellect; it is also the model for rational souls to understand and to emulate.

Aristotle’s natural philosophy

As an encyclopedia scientist, Aristotle has developed a lifelong interest in the study and made a long-term impact to almost every subject. His writing involves subjects such as ethics, metaphysics, psychology, and the law of Athens, which constructed the opening all-inclusive system of western philosophy, including ethics, aesthetics, logic and science, politics and metaphysics. Aristotle and his works became the foundation for the both religion and science, especially through the Middle Ages. In religion, Aristotelian ethics were known as the base for St. Thomas Aquinas' works that motivated Christian thought on free will. In science, Aristotle believed that the movement of celestial bodies is a material entity. The earth is spherical, which is the center of the universe. Earth and other body consist by other elements. The material on earth is four elements, moisture, fire, earth, and celestial body is composed of the five elements "Ether". What’s more, Aristotle's empirical approach based on observation, hypothesis and direct experience (experimentation) is the basis for scientific activity in nearly every field of study.

Aristotle provides detailed descriptions on physical science in two main parts, the first one concentrating on an inquiry into nature and the second focusing on motion. Compared with Plato, Aristotle’s contributions to science were far more profound. This is because he creates an early form of scientific research to observe the world. Even though this method has been changed through history, yet the essence remains almost the same. In contrast with Plato’s idealistic philosophy, Aristotle favored the direct observation and experience. For Aristotle, the best way to see reality is to walk out of the cave and experience the direct light, rather than depending on indirect image or internal experiences. In science, Plato combined mathematics, geometry with physics, yet his work was more in conceptual level than actually applicable. However, Aristotle is considered to one of the first true scientists. He brought new insights into physics, math and geometry.

Since motion is mentioned in the definition of nature, any discussion of nature will need to explore motion. In Physics, Aristotle mainly discusses the issue of motion, therefore establishing his own argument of motion. Motion and change are closely intertwined in Aristotelian physics. According to Aristotle, Motion involves a change from potentiality to actuality. Generally, his motion theory consists of four elements: the essence of motion, the category of motion, the condition of motion, and mover. Here Aristotle characterizes the links which motions fall into different categories and discoveries the intertwined effect and changes. Aristotle claims that changes of relations are not changes spontaneously; on the contrary, they are fortuitous, as they happen also in objects in which no change occurs at all. As a result, the fundamental two categories of action and passion can be removed: Since there are no motions of motions, we can put aside action and passion in the Categories. As a result, it leaves us with a shorter list of relevant categories, (1) substance, (2) quality, (3) quantity, and (4) place. Aristotle also pointed out that the speed at which two similar objects fall is proportional to their weights and the density at which they move. Aristotle said that every moving thing must have an object that pushes it forward. On this sense, there must be a first mover that generates all the movement, namely, the existence of supernatural power. Such an entity has to possess an infinite power which it communicates to the moved celestial sphere. Hence, this entity cannot be divisible and cannot have extension (Physics 8.10).

Conclusion

This paper briefly concludes Plato’s philosophy on natural science and knowledge, and compares his views with Aristotle’s. Both have made tremendous contribution to philosophy, natural sciences, politics and other subjects. In the book Timaeus, Plato provides a detailed description of the formation of the universe. He proposes that the universe is the handwork of a divine Craftsman who imposes an order on an existent chaos. Aristotle, on the other hand, developed Plato’s perspectives on natural science, yet put forward his own ideas on the concept of motion.